Radioactive sources are increasingly prevalent in modern society. Radioactive sources provide many benefits as well as risks such as accidental exposure, loss or pilferage of the sources, and clandestine transport of nuclear weapon materials, among other risks. Nations must be able to detect radioactive sources and to determine their locations, despite ubiquitous background radiation from cosmic rays and benign environmental sources. In addition, radioactive material from a spill or accident must be localized for removal or avoidance. Search personnel are subject to continuous exposure to radiation while attempting to localize a lost or hidden source. Determining the direction toward a source would greatly speed up the search process, thereby rapidly localizing sources that may otherwise be missed, and minimizing the dose absorbed by personnel.
What is needed is a compact, rugged, light-weight, efficient detector that indicates the specific direction of a source of gamma rays or neutrons, without extensive searching or iteration. Preferably the new detector would have sufficient sensitivity to detect both large and small sources, with sufficient angular precision to localize the source among clutter and obfuscation, rapidly, with high efficiency, and at low cost.